The present invention relates to an Alpine ski. An Alpine ski has a front area known as the tip, a rear area known as the tail, and an intermediate area known as the mid-section.
FIG. 1 of the schematic drawing attached is a profile view of an Alpine ski wherein the tip area, mid-section, and tail area are designated by reference numerals 2, 3, and 4. This FIG. 1 also shows that the thickness of the ski varies over its length, the thickness being substantially greater in the mid-section than in the end areas, namely the tip and tail areas. This is because the binding of the skier""s boot is mounted in the mid-section area. Hence this area has to be the strongest, and it is through this mid-section that most of the forces between the snow and the skier""s boot pass.
As a result of this design, the rigidity of the ski, i.e. the resistance to flexing, is not constant over the entire length of the ski. As shown in FIG. 2, which is a curve of the ski length on the abscissa axis plotted against the rigidity on the ordinate axis, the rigidity of the ski is far greater in the mid-section (P) than in the tip (S) and tail (T) areas. That fact that the binding is mounted in the mid-section, and that ski boots with very rigid soles are used, increases the rigidity still further relative to the rigidity of the ski considered alone. As a result, the difficulty in turning with the ski is increased.
The rigidity of a ski is measured as follows: the ski is placed flat between two supports with a distance of L (200 to 600 mm) between them and a load F of 40 to 60 kg is applied half-way between these supports. The deformation of the ski under this load (flex) is then measured. The ski is then moved so that this measurement can be made on another area (moved between 50 and 200 mm). The different flex values define the rigidity curve shown in FIG. 2.
To offset this rigidity added by the boot-binding assembly in the mid-section, the idea was evolved of mounting the binding, namely a stop and a heelpiece, not directly on the ski but on an intermediate plate attached locally to the ski, at one of its ends for example, and mounted with the possibility of sliding on the ski, allowing release. Such a plate is known from document CH 671,887. This release function effectively eliminates the influence of the tension springs of the heelpiece on the boot sole, increasing the bending of the ski, but nonetheless, because of its own rigidity, such a plate increases the rigidity of the ski. Making a plate to mount a boot binding that has notches favoring its flexing is also known. Such a plate is disclosed in document FR 2,763,861.
However, by returning flexibility to this plate, the concept of release became lost; moreover this solution requires the use of a plate that increases the weight of the ski-binding assembly.
The goal of the invention is to define the rigidity of a bare ski while anticipating the influence of the binding-boot assembly required for the ski to be used.
For this purpose, the Alpine ski to which it relates, the rigidity, namely the resistance to flexing in the lengthwise direction of the ski, of the center part of the mid-section is less than the rigidity in the two end parts of the mid-section, namely the parts that connect with the front and rear areas.
Hence, this ski is distinguished from a classical Alpine ski in which the rigidity curve, namely the resistance to flexing in the lengthwise direction of the ski placed flat between two supports, is practically a function of the change in thickness of the ski, namely the rigidity increases overall from the ends to the central area of the mid-section.
Advantageously, in the center part of the mid-section, the rigidity is at least 5% less than the lowest rigidity of the end parts of the mid-section.
The fact of reducing the rigidity in the center part of the mid-section enables the rigidity to be made uniform over the length of the mid-section, after taking into account the stiffening effect of the boot mounted inside the binding.
A number of solutions have been put into practice for decreasing rigidity with various ski designs: in the case of a traditional-design ski, namely having a lower assembly, strong longitudinal walls called sides, disposed on either side of a central core, and an upper assembly; in the case of a shell ski, i.e. a ski with an outer envelope made of synthetic material reinforced on the inside of the ski by at least one layer of stratified fabric, forming the upper wall and the side walls of the ski, and whose borders rest directly or indirectly on the edges; or in the case of a mixed-design ski, namely having a shell whose borders rest on lengthwise reinforcing elements, present at least in the center part or mid-section of the ski.
According to a first embodiment of this ski, in the case where it has lengthwise reinforcing elements visible on the side walls of the ski and called sides, the decrease in rigidity in the mid-section of the ski is achieved by a localized decrease in the height or the thickness of the sides.
In this case, the localized decrease in the height of the sides may be total, and may result in an interruption in the center part of the mid-section.
According to a second possibility, the decrease in rigidity in the center part of the mid-section is achieved by a localized reduction in the width of the upper part of the ski, with the lower part comprising the sole and the edges continuing to be of the traditional width.
According to a third possibility, the decreased rigidity in the center part of the mid-section is achieved by locally reducing the distance between the upper and/or lower reinforcements and the neutral fiber of the ski.
According to another possibility, the decreased rigidity in the center part of the mid-section is achieved by locally reducing the thickness of the ski.
According to one embodiment of the ski according to the invention, where its design comprises a shell made of synthetic material reinforced on the inside of the ski by at least one layer of stratified fabric, forming the upper wall and part of the side walls of the ski whose borders rest on lengthwise reinforcing elements visible on the side walls of the ski, and which rest directly or indirectly on the edges, the decrease in rigidity in the mid-section of the ski is achieved by reducing the height or locally suppressing the lengthwise reinforcing elements while increasing the height of the side walls of the shell in this area.
Whatever the ski design, the length of the reduced rigidity area is approximately 200 mm to 600 mm, preferably between 400 and 500 mm.